Lightbulb



FIG. 1 is a perspective view of the lightbulb showing my new design;

FIG. 2 is a side elevational view of the lightbulb;

FIG. 3 is a plane view of the lightbulb; and,

FIG. 4 is a view of the bottom of the lightbulb.

The ornamental design for the lightbulb, as shown and described.